2-(o-nitrosophenyl)-2,1,3-benzotriazole



United States Patent 01 hce 3,517,025 2-(0-NITROSOPHENYL)-2,1,3-BENZOTRIAZOLE Rudolph Anthony Carboni, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Apr. 21, 1967, Ser. No. 634,056

. Int. Cl. C07d 55/04 US. Cl. 260-308 1 Claim ABSTRACT OF THE DISCLOSURE This invention relates to 2-(o-nitrosophenyl)-2,1,3- benzotriazole and a process for its manufacture.

BACKGROUND OF THE INVENTION 2,3,5,6dibenzo1,3a,4,6a-tetraazapentalene is a compound which can be used as an intermediate in the preparation of tetranitro 2,3,5,6dibenzo-1,3a,4,6a-tetraazapentalene, a widely used explosive composition. 2,3,5,6- dibenzo-1,3a,4,6a-tetraazapentalene, the intermediate, has heretofore been available by controlled thermal decomposition of o,o'diazidoazobenzene. That synthesis requires the preparation of o,o'-diaminoazobenzene and conversion of this to the corresponding o,o'-diazidoazobenzene, which then is thermally decomposed to form the tetraazapentalene. The preparation of the 0,0- diazidoazobenzene, however, is difficult and somewhat costly.

SUMMARY OF THE INVENTION A need therefore exists for a compound which can be easily synthesized and readily converted to 2,3,5,6-dibenzo-1,3a,4,6a-tetraazapentalene. The instant invention provides such a compound, 2-(o-nitrosophenyl)-2,1,3- benzotriazole, and a process for its preparation. The compound of this invention has the structural formula:

The process for its preparation comprises contacting 2- (o-aminophenyl)-2,1,3-benzotriazole with an oxidizing agent, preferably selected from the group consisting of peracetic acid (peroxyacetic acid), hydrogen peroxide, and alkali metal persulfates and preferably at temperatures of less than about 110 C.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The starting material for the process of the instant invention is 2-(o-amin0phenyl)-2,1,3-benzotriazole, which can be obtained by the process described in British Pat. 922,943, which patent is hereby incorporated by reference. This compound is preferably placed in solution in a solvent which is non-reactive with the reagents used in this process, and has a boiling point of about from 35 to 180 C. Such solvents include, for example, halogenated hydrocarbons such as methylene chloride, carbon tetrachloride, trichlorofluoromethane, trichlorotrifiuoroethane, dibromo tetrafluoroethane, chloroform and other haloalkanes. Of these, chloroform is especially preferred because of its inertness toward the reagents of this process, its convenient boiling point, and ready availability. The quantity of solvent used is not critical to this invention; however, suflicient solvent should be used to place all of the expected reaction product in solution. Usually -10 ml. of solvent/gram of starting material is a sufiicient quantity for the purposes of this process.

The oxidizing agents which can be used in this process include any strong oxidizing agent which will oxidize the ammo group to a nitroso group without further change of the starting material. Oxidizing agents preferred for this process include, for example, peracetic acid, hydrogen peroxide, and alkali metal sulfates such as potassium persulfate, sodium persulfate, and potassium monopersulfate, of which peracetic acid is particularly preferred.

The oxidizing agent can optionally be placed in solution for more complete dispersion of the oxidizing agent throughout the solution of starting material. The solvent used for the oxidizing agent should be selected with consideration for its compatability with the oxidizing agent itself. For example, if peracetic acid is selected as the oxidizing agent, acetic acid is particularly suitable as a solvent, since the peracetic acid usually is prepared in acetic acid and is relatively stable in this solvent.

The process of the instant invention can be initiated at ambient temperatures, but an elevated temperature is preferred. The temperature of the reaction mixture preferably is regulated so as to not exceed C.

The quantity of oxidizing agent used in the instant process is not critical to this invention. However, an adequate amount of oxidizing agent should be used to insure complete oxidation without significant over oxidation of the starting material. Generally, sufficient oxidizing agent is used to furnish two atoms of active oxygen for each mol of aminophenylbenzotriazole present in the reaction mixture.

After completion of the addition of oxidizing agent, the reaction mixture preferably is maintained at an elevated temperature, generally not exceeding 110 C. and usually limited by the reflux temperature for the mixtures containing lower boiling solvents, e.g., chloroform, until the oxidation is complete. The reaction is usually completed within a period of about from 1 to 2 hours. The desired product can be recovered from the reaction mixture and purified by methods well known to those skilled in the art. For example, the cooled and stirred reaction mixture can be made basic with a slight excess of aqueous sodium hydroxide to neutralize the acidic reaction mixture, whereupon the 2-(o-nitrosopheny1)-2,1,3- benzotriazole passesinto the lower chloroform layer, which is separated from the upper aqueous layer, and the chloroform is evaporated leaving the nitrosocompound. Further purification can include washing with water and recrystallization from additional solvent. Analysis indicates that the compound of this invention exists as a dimer in the solid state, as is frequently found in nitroso compounds. However, the reaction properties, for example, in the formation of dibenzo-1,3a,4,6a-tetraazapentalene, are characteristic of the monomeric compound.

2-(o-nitrosophenyl)-2,1,3 benzotriazole can be converted to 2,3,5,6 dibenzo 1,3a,4,6a-tetraazapentalene by contacting the nitrosophenylbenzotriazole with a trialkyl phosphite in the presence of a solvent at elevated temperatures. For example, the nitrosophenylbenzotriazole can be contacted with triethylphosphite in benzene solution and heated to reflux for 30 minutes. The tetraazapentalene thus obtained can then be converted to tetranitrotetraazapentalene according to the process set forth in British Pat. 930,304. As indicated in the British patent, which is incorporated herein by reference, the tetranitrotetraazapentalene is an explosive which is particularly useful in high temperature applications.

In the following example, which further illustrates the instant invention, parts and percentages are by weight unless otherwise indicated.

3 EXAMPLE To a stirred solution of 8.3 parts of 2-(o-aminophenyl)-2,1,3-benzotriazole in 150 parts of chloroform, in a glass reactor surrounded by a mixture of ice and water, is added a solution of 13.8 parts of 40% peracetic acid (i.e., acetic acid containing 40% by weight of peracetic acid, sometimes more properly identified as peroxyacetic acid) in 40 parts of acetic acid. After 15 minutes a bright yellow solid separates. The ice-bath is removed and stirring is continued for one hour, after which the mixture is heated to reflux temperature for 45 minutes, cooled to room temperature, and poured into cold water. The water layer is decanted, replaced with fresh water which is mixed, allowed to layer out and decanted. Sufficient 20% NaOH solution is added to the chloroform layer to make it slightly alkaline. The mass of liquid is filtered to remove solid which separates. The solid (5.3 parts) after washing with water and chloroform, and drying, is recrystallized from chloroform to give a crop of pale yellow, hairlike needles which melt at 185-1855 C. The identity of the product as 2-(0- nitrosophenyl) 2,1,3 benzotriazole is confirmed by elemental analysis, molecular weight determination in ethylene chloride, and by spectral analysis.

Calcd. for C H N4O (Percent): C, 64.28; H, 3.60;

4 N, 2499; Mol. wt. 224. Found (Percent): C, 63.96; H, 3.72; N, 24.56; Mol. wt., 229.

The ultraviolet spectrum in ethanol shows a weak maximum at 740 ITl,lL( 45) and a strong absorption at 284 In,w(e 18,500) and 227 1T1,u(e 22,600). The infrared spectrum of the solid shows a strong band at 7.87;. which is characteristic of nitroso dimers, thus indicating that the compund of the invention in the solid state exists as a dimeric material.

What is claimed is:

1. 2-(o-nitrosophenyl)-2,1,3-benzotriazole.

References Cited UNITED STATES PATENTS 3,262,943 7/1966 Kauer.

FOREIGN PATENTS 922,943 4/1963 Great Britain.

OTHER REFERENCES Smith, Open-Chain Nitrogen Compounds, vol. 2, (New York, 1966), p. 379.

ALTON D. ROLLINS, Primary Examiner 

